Neutron capture therapy is an attractive alternative to standard radiation techniques for cancer treatment, if nuclei such as 10B, can be selectively concentrated in tumors. Small, unilamellar phospholipids vesicles are known to be taken up by animal and human tumors. Liposome formulations will be tested for their ability to stably encapsulate high concentrations of boron compounds. Biodistribution of these B-containing liposomes will be tested in mice bearing EMT6 tumors using radioiodine-labeled Na2 B10 H10.